The men of Worcester celebrated his arrival by a raid on the men of Wilts.

"On that ilk day," says the Chronicle, "rode AEthelhund, ealdorman of the Huiccias [who were Mercians], over at Cynemaeres ford; and there Weohstan the ealdorman met him with the Wilts men [who were West Saxons:] and there was a muckle fight, and both ealdormen were slain, and the Wilts men won the day." For twenty years, Ecgberht was engaged in consolidating his ancestral dominions: but at the end of that time, he found himself able to attack the Mercians, who had lost Offa six years before Ecgberht's return.

In 825, the West Saxons met the Mercian host at Ellandun, "and Ecgberht gained the day, and there was muckle slaughter." Therefore all the Saxon name, held tributary by the Mercians, gathered about the Saxon champion.

"The Kentish folk, and they of Surrey, and the South Saxons, and the East Saxons turned to him." In the same year, the East Anglians, anxious to avoid the power of Mercia, "sought Ecgberht for peace and for aid." Beornwulf, the Mercian king, marched against his revolted tributaries: but the East Anglians fought him stoutly, and slew him and his successor in two battles.

Ecgberht followed up this step by annexing Mercia in 829: after which he marched northward against the Northumbrians, who at once "offered him obedience and peace; and they thereupon parted." One year later, Ecgberht led an army against the northern Welsh, and "reduced them to humble obedience." Thus the West Saxon kingdom absorbed all the others, at least so far as a loose over-lordship was concerned.